1. Field of the Invention
The invention relates to a method for manually aligning ophthalmic spectacle lenses, in particular semifinished products of progressive lenses, the spectacle lens being held on one side for the purpose of machining the free side of the spectacle lens by a holder via a connecting material situated therebetween, and the holder being inserted into a cut-out of a retaining device. The invention also relates to an apparatus for manually aligning ophthalmic spectacle lenses.
2. Description of the Related Art
The method known from practice and applied in order to align a spectacle lens for subsequent blocking onto a holder for further machining is performed by stamping on a marking and subsequently aligning the spectacle lens with the aid of this stamped marking. The position of the marking on the spectacle lens is prescribed by two marks introduced into the spectacle lens. Simple semifinished products that are machined only on one side of the spectacle lens already have this marking applied.
In the case of individual spectacle lenses, both sides of the semifinished product can be machined. For this reason, it is necessary after the machining of a first side for the semifinished product to be placed on a new holder for the purpose of machining the second side. In this process, on the second holder the spectacle lens must exhibit exactly the same positioning in the plane perpendicular to the optical axis as on the first holder. This requires the spectacle lens to be released from its holder after the first machining process and cleaned so that the marking can be stamped onto the spectacle lens for the alignment of the second holder.
This method has the disadvantage that a new placement of a marking and the later alignment with the aid of this marking are subject to certain tolerances. Likewise, cleaning before stamping the marking is a time—consuming and cost—intensive production process.
DE 696 06 340 T2 discloses a method for producing an ocular lens, the lens material being aligned with the block by rotating the lens material and the block relative to one another. The workspindle of the first machining device is rotated, the block being movable in directions orthogonal to a rotation axis of the workspindle of the first machining device. An ultraviolet curing adhesive agent is used in this case as adhesive agent, ultraviolet rays being radiated onto the lens material and the block after the lens material has been aligned with the block. The lens material is clamped by means of a loader while it is being guided by a chuck of a workspindle of a device for machining inner surfaces. The ultraviolet curing adhesive agent is dripped onto a surface of the block that is to be bonded. Thereafter, the bonding surface of the block is arranged in an alignment operation such that the bonding surface overlaps with the machined surface of the lens material. The block and the lens material are thus aligned relative to one another, while being caused to rotate relative to one another by slow rotation of the workspindle. UV irradiation is required to bond the block to the lens material. A surface of the lens material can be machined thereafter.
Utility model DE 297 23 542 U1 discloses an apparatus for machining optical lenses. Such an apparatus is related, in particular, to the grinding of lens blanks. The lens blank is inserted into a chucking tool of a workpiece spindle and clamped mechanically on its clamping shoulder by means of an automatically actuable chucking tool, the chucking tool being a vacuum-assisted collet chuck. A coarse grinding tool on the workpiece spindle can be used to grind the lens body coarsely. After machining of a first side, the same apparatus can likewise be used to machine the second side.
Although the utility model DE 297 23 542 U1 relates to mineral lenses, the abovenamed apparatus cannot be used for spectacle lenses. After the machining of one surface, the lens is rotated and clamped at the circular circumference in a workpiece spindle for the machining of the second surface. However, this is not possible for spectacle lenses since, particularly in the case of spectacle lenses for correcting hyperopie it is necessary for these to be produced with as thin a rim as possible, for which reason they cannot be machined at the rim or in the vicinity of the rim. Then, there would be a very high risk of damaging the spectacle lens by the operation of clamping the thin rim. It is therefore impossible to use the apparatus and/or the method advised above for spectacle lenses. It is likewise disadvantageous that spectacle lenses which are to exhibit a reduction in central thickness, as a result of which the rim must exhibit a free form profile, cannot be clamped in a collet chuck.